1. Field of the Invention
The present invention relates to a liquid discharge head that discharges a desired liquid by the creation of bubbles generated by thermal energy acting upon the liquid, and also, to a method of manufacture therefor. More particularly, the invention relates to a liquid discharge head provided with the movable member which is displaceable by the utilization of the creation of bubbles, and to a method of manufacture therefor as well.
In this respect, the term "recording" in the description of the present invention means not only the provision of images having characters, graphics, or other meaningful representation, but also, the provision of those images that do not present any particular meaning, such as patterns.
2. Related Background Art
There has been known the so-called bubble jet recording method, which is an ink jet recording method whereby to form images on a recording medium by discharging ink from discharge port using acting force exerted by the change of states of ink accompanied by the abrupt voluminal changes (creation of bubbles), and to form images on a recording medium by the discharged ink that adheres to it. For the recording apparatus that uses the bubble jet recording method, it is generally practiced to provide, as disclosed in the specifications of Japanese Patent Publication No. 61-59911 and Japanese Patent Publication No. 61-59914, the discharge port that discharge ink, the ink paths communicated with the discharge port, and heat generating member (electrothermal transducing devices) arranged in each of the ink paths, which serve as means for generating energy for discharging ink.
In accordance with such recording method, it is possible to record high quality images at high speeds with a lesser amount of noises. At the same time, the head that executes this recording method makes it possible to arrange the discharge port for discharging ink in high density, with the excellent advantage, among many others, that images are made recordable in high resolution, and that color images are easily obtainable by use of a smaller apparatus. In recent years, therefore, the bubble jet recording method has been widely utilized for a printer, a copying machine, a facsimile equipment, and many other office equipment. Further, this method is utilized for the industrial use, such a textile printing system.
In this respect, some of the inventors hereof have ardently studied the principle of liquid discharge again for the provision of a new liquid discharge method that utilizes the bubbles that have never been obtained by the application of conventional art, as well as the head which is usable for such method, and have applied for a patent as described in the specification of Japanese Patent Application No. 8-4892.
The patent described in the specification of Japanese Patent Application No. 8-4892 is a technique such as to control bubbles positively by arranging the positional relations between the fulcrum and the free end of the movable member in each liquid flow path so that the free end is positioned on the discharge port side, that is, on the downstream side, and that the movable member is positioned to face each heat generating device or bubble generating area.
By use of the liquid discharge head or the like formed in accordance with the extremely new discharge principle as described above, it becomes possible to obtain the synergic effect produced by the created bubbles and the movable member which is caused to be displaced thereby. As a result, liquid in the vicinity of the discharge port is discharged more effectively, and as compared with the conventional discharge method of bubble jet type and heads, the discharge efficiency is enhanced significantly.
With the durability and the responsiveness to the high frequency in view, it is preferable for the discharge method and the apparatus that use the aforesaid movable member to be able to discharge liquid in good condition irrespective of the kinds of liquid, and also, to structure the movable member with the metallic material which gives elasticity at least a part (only on the external surface, only in the interior, or of the entire body).
When the free end of the movable member is structured in a cantilever fashion, the portion on its fulcrum side should be structured so that it is fixed in anyway. For the formation of such a structure of fixation, it is conceivable to use gold bonding or adhesive agent or a mechanical coupling element (such as a screw) to fix the movable member to a pedestal.
However, in a case where the metallic part of the movable member is structured with the metallic material that has been selected from the viewpoint of the elasticity, the durability, or of the easier manufacturing process, and if such selected metal is different from the those metallic materials used for the pedestal or the structure of fixation, a condition may ensue that electrolytic corrosion occurs between them when becoming electrically conductive (due to the direct contact or through the pin holes of resin or the coating layer). If the movable member is left intact under such condition, the property of the movable member may change due to the structural changes thereof (decreased or increased). Consequently, it is conceivable that the discharge characteristics are caused to change accordingly.
The inventors hereof have realized as one of the new objectives that the reliability of the movable member should be maintained stably for a long time under such condition.
Also, it may be expected that with the structure having the movable member arranged in the liquid flow path, which requires the consideration of the properties of the materials used each for the surface to be in contact with liquid and the external layer thereof, respectively, the conductive condition described above may result indirectly depending on the components of the liquid, not necessarily to be in the condition where those portions become electrically conductive directly. In other words, the content of metallic ion or some other ion in the liquid may bring about the condition that causes electrolytic corrosion eventually. Conceivably, an ion of the kind may reside in the liquid flow path due to the structure of a liquid retainer serving as the liquid supply source or due to the use of liquid other than those designated ones. Therefore, it is the second objectives that the reliability of the movable member should be maintained stably for a long time even under such condition as described above.
In consideration of the supporting structure of the movable member, it is also another one of the objectives from the different viewpoint that the structure should be provided in order to enhance the closer contact between the movable member and the pedestal, and also, to the contact between them stronger.